THE last time a Fianna Fáil taoiseach lost his minister for defence, he himself was gone from the top job within 90 days. Twenty years ago, Jim McDaid, newly appointed to the cabinet, was forced out, and three months later Charles Haughey was deposed.

Willie O'Dea's departure shouldn't have anything like the same impact on Brian Cowen, but history does show that when a ministerial head is delivered on a plate, it seriously destabilises a coalition – never more so than in 1990, when the Progressive Democrats forced the resignation of yet another defence minister, Brian Lenihan senior, over the controversy about phone calls to Áras an Uachtaráin nearly a decade earlier. The PDs' action caused enormous bitterness among Fianna Fáil deputies.

But the circumstances, Fianna Fáil TDs say, are very different this time. While there is some irritation towards the Greens for forcing Willie O'Dea's departure, the view is that the Limerick poll-topper was, in the main, the author of his misfortune.

O'Dea is respected, particularly for his willingness to go out and bat for the party regardless of how tough the circumstances, an approach that has seen him referred to as the government's very own St Jude, the patron saint of hopeless causes. He is also liked, particularly because of his biting sense of humour. But he isn't particularly seen as a team player in the parliamentary party.

"Willie O'Dea isn't Brian Lenihan senior," said one senior deputy. "Brian was Mister Popular, a presidential candidate whose nationwide tour drew crowds of thousands. Willie wouldn't be in that category. He is purely interested in Limerick. He made no effort nationally. On that basis the damage to the government will be short-term," he said.

Whether that view is shared by O'Dea's cabinet colleagues, especially his friend, Taoiseach Brian Cowen, is moot.

While relations between Cowen and the Green leadership have been very good to date, it remains to be seen what impact the Greens' intervention in the O'Dea affair will have. Cowen is a much more sophisticated politician now than he was in the days when, referring to Fianna Fáil's then coalition partners the PDs, he declared to the adoring ard fheis crowds: "If in doubt leave them out". But he is Fianna Fáil to his fingertips and he won't have liked the Greens putting down a marker in relation to one of his ministers, even if, deep down, he knows the junior coalition party had little option.

The impact it will have on the Greens themselves will also be watched closely. The party made a conscious decision on entering government that it wasn't going to be a watchdog for Fianna Fáil. While this strategy has at times horrified some of the party die-hards who regard the senior coalition partner with distaste, it was pragmatic and sensible. Coalition governments, like any other relationship, cannot work if one party is constantly publicly correcting the other.

But the previously muzzled Green watchdog certainly barked when it came to Willie O'Dea. Now that the Greens have barked once, there will be even more pressure on them to bark again, if and when the next contentious issue arises.

Dan Boyle's very public role in O'Dea's departure will mean he is certain to be targeted by the opposition parties in such circumstances. How will he react to that? To be fair to Boyle, he may have felt quite rightly last week that this was simply one issue where the Greens had to take a stand. But frequent tweets like the one about O'Dea will be like a red rag to a bull for Fianna Fáil.

Ultimately, what should keep the two coalition partners together is the genuine collegiality that certainly exists at the top between the two parties as well as, more importantly, political pragmatism.

Neither party can afford to face the electorate for some time. Fianna Fáil would lose a couple of dozen seats in an election, while the Greens would at best be left to one or two. The Greens are determined to stay in power, because they see this as, perhaps, a once-in-a-lifetime opportunity to implement the Green policies they so passionately believe can help improve the country. Fianna Fáil ministers will be equally determined to stay in power because that is who they are – it's in their DNA.

The past two weeks have demonstrated yet again that making predictions in politics is a hazardous game. But the likelihood is that, despite the claims from the opposition that the government is on its last legs, the coalition will regather and move on. It has certainly been wounded by the loss of O'Dea but, for now at least, that wound is nowhere near deep enough to be fatal.